Matrix injector driver circuit

ABSTRACT

A fuel injector control circuit reduces the number of gates required by arranging high side and low side gates in a matrix. Each coil is selectively activated by activating a unique pair of a high side gate and a low side gate, thus reducing the total number of gates required.

RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 09/703,537, filed onNov. 1, 2000, which claims priority to U.S. Provisional Application No.60/162,839, which was filed Nov. 1, 1999.

BACKGROUND OF THE INVENTION

The present invention relates generally to fuel injector controlcircuits.

Known fuel injector control circuits generally comprise an open coil anda close coil for each fuel injector. To inject fuel into the cylinder,it is necessary to activate the open coil and then the close coil. Someapplications require that the close coil on a given cylinder beactivated before the associated open coil is deactivated. This is knownas simultaneous excitation.

Known fuel injector fuel circuits connect each coil to the power supplywith a different switch (such as a FET or other gate). Thus, for an 8cylinder engine, 16 high side gates were required, each with associateddrive circuitry.

When a coil is energized, some energy is stored in a magnetic field thatsurrounds the coil. When the coil is de-energized, it is desirable torecover some of the energy that was stored in the magnetic field. Thisenergy recovered is done by a known technique called “recirculation.”

SUMMARY OF THE INVENTION

The present invention provides cost saving by reducing the number ofhigh side gates and the associated drive circuitry from 16 to as few as4 (for an eight cylinder engine). Various configurations are illustratedherein, with different benefits and features in each. However, as ageneral principal, each of these utilizes high and low side gates whichselectively activate selected coils via a matrix.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a high-level schematic of the fuel injector control system ofthe present invention;

FIG. 2 is a schematic for a first circuit for controlling coilsaccording to the present invention;

FIG. 3 is a schematic of a second, alternate circuit for controllingcoils according to the present invention;

FIG. 4 is a schematic for a third circuit for controlling coilsaccording to the present invention.

FIG. 5 is a schematic of a fourth alternate circuit for controllingcoils and according to the present invention;

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

A fuel injector control circuit 20 is shown schematically in FIG. 1. Amicrocontroller 22 is programmed generally to control high side drivers24 to drive high side gates 26 and low side drivers 28 to drive low sidegates 30. The high side gates 26 and low sides gates 30 selectivelyactivate coils 32, which in turn selectively activate injectors 34.

Generally, the present invention reduces the number of high side gates26. This is accomplished by treating the coils as a matrix, wherein eachcoil is selected by selective activation of one of the high side gatesand one of the low side gates.

For example, a first circuit 40 is shown generally in FIG. 2, includinghigh side gates 26, including gates Q1, Q2, Q5, Q6, Q9, Q10, Q13, Q14.The circuit 40 further includes low side gates 30, including Q17-Q20.This circuit 40 illustrates 16 coils OC_A-H and CC_A-H. In the circuit40, high side gate Q1 connects odd coil OC_A and odd coil CC_Aselectively to power supply. In circuit 40, each of the high sidedrivers connects the open coil and associated close coil for one of the8 injectors.

The low side gates 30, Q17-Q120 selectively connect different groups ofthe coils to ground. For example, as can be seen in FIG. 2, Q17selectively connects the odd open coils, Q18 selectively connects theodd close coils, Q19 selectively connects the even open coils and Q20selectively connects the even close coils. Thus, any one of the 16 coilscan be selectively individually activated by switching on the properpair of a high side gate 26 and a low side gate 30. The diodes D1-D16are placed in series with each coil and prevent interaction between thecoils. The operation of the first circuit 40 is further demonstrated inthe following table.

TABLE 1 Q17 Low Q18 Low Q19 Low Q20 Low side driver side driver sidedriver side driver for odd for odd for even for even open coils closecoils open coils open coils Q1 High side OC_A CC_A driver for cyl. A Q2High side OC_B CC_B driver for cyl. B Q5 High side OC_C CC_C driver forcyl. D Q6 High side OC_D CC_D driver for cyl. D. Q9 High side OC_E CC_Edriver for cyl. E Q10 High side OC_F CC_F driver for cyl. F Q13 Highside OC_G CC_G driver for cyl. G Q14 High side OC_H CC_H driver for cyl.H

In this example, because gates are connected on common points on thehigh side of open and close coils in the same cylinder, simultaneousexcitation cannot be performed. On the other hand, the advantages ofthis configuration include that the failure of one high side gate willonly disable one cylinder and that three wire coils (with the high sideconnection with both open and close coils on the same wire) can be used.

A preferred method and apparatus for controlling of low side gates 30 isdisclosed in co-pending patent application U.S. Ser. No. 09/703,537entitled “CONTROL OF DRIVER CURRENT VIA LOW SIDE GATES” filed on Nov. 1,2000, the assignee and inventors of which are the same as the assigneeand inventors of this patent application, and which is herebyincorporated by reference fully as if repeated herein.

FIG. 3 illustrates a second circuit for activating the coils. As can beseen, the second circuit 50 requires only 4 high side gates. In thecircuit 50, each of the high side gates, Q1, Q5, Q9 and Q13 operates theopen and close coils for two cylinders. Low side gates 30, Q17-Q20,operate identically as in FIG. 2. Thus in this circuit 50, any of thecoils can be selectively activated by switching the appropriate pair ofhigh and low side gates. This is shown in the Table 2 below.

TABLE 2 Q17 Low Q18 Low Q19 Low Q20 Low side driver side driver sidedriver side driver for odd for odd for even for even open coils closecoils open coils open coils Q1 High side OC_A CC_A OC_B CC_ B driver forcyl. A and B Q5 High side OC_C CC_C OC_D CC_ D driver for cyl. C and DQ9 High side OC_E CC_E OC_F CC_F driver for cyl. E and F Q13 High sideOC_G CC_G OC_H CC_ H driver for cyl. G and H

Some advantages of this configuration are that the failure of one highside FET will only disable two cylinders, this configuration onlyutilizes four high side gates and that this version allows the use ofthree wire coils. The disadvantage of this configuration is thatsimultaneous excitation of the open and close coils on the same cylinderis not possible.

FIG. 4 illustrates a third circuit 60 for operating the fuel injectorcoils for operating. In this third circuit 60, 8 high side gates Q1, Q2,Q5, Q6, Q9, Q10, Q14 are no longer connected to two coils in the samecylinder (as in FIG. 3). Rather, each high side gate Q1, Q5, Q9, Q13 isconnected to a pair of open coils (one even, one odd), while the gatesQ2, Q6, Q10 and Q14 are connected to a pair of close coils (one even,one odd). The low side gates 30 operate as described above with respectto FIG. 1 in this third circuit 60. Because the open and close coils onany cylinder do not share any high side driver, simultaneouslyexcitation can be utilized. The operation of this circuit 60 is furtherdescribed in the Table 3, below.

TABLE 3 Q17 Low Q18 Low Q19 Low Q20 Low side driver side driver sidedriver side driver for odd for odd for even for even open coils closecoils open coils open cells Q1 High side OC_A OC_B driver for cyl. A andB open coils Q2 High side CC_A CC_B driver for cyl. A and B close coilsQ5 High side OC_C OC_D driver for cyl. C and D open coils Q6 High sideCC_C CC_D driver for cyl. C and D close Q9 High side OC_E OC_F driverfor cyl. E and F open coils Q10 High side CC_E CC_F driver for cyl. Eand F close coils Q13 High side OC_G OC_H driver for cyl. G and H opencoils Q14 High side CC_G CC_H driver for cyl. G and H close

FIG. 5 illustrates a fourth schematic 70 including 4 high side gates,Q1, Q5, Q9 and Q13. High side gate Q1 selectively connects open coils A,B, C, D to power supply, while Q5 selectively connects close coils A, B,C, D. Similarly, gate Q9 selectively connects open coils E, F, G, H tothe power supply while gate Q13 selectively connects close coils E, F,G, H to the power supply. In schematic 70, the low side gates 30 areconfigured differently, as shown. Gate Q17 selectively connects opencoils 1 and 5 and close coils 2 and 6 to ground. The operation of theremaining gates and activation of the remaining coils are illustrated inthe following table as well as in schematic FIG. 5.

TABLE 4 High Side High Side High Side High Side Driver Q1 Driver Q5Driver Q9 Driver Q13 1-4 1-4 5-8 5-8 Open Coils Close Coils Open CoilsClose Coils Low Side Open Coil Close Coil Open Coil Close Coil DriverQ17 #1 #2 #5 #6 1 and 5 Open 2 and 6 Close Low Side Open Coil Close CoilOpen Coil Close Coil Driver Q18 #2 #1 #6 #5 2 and 6 Open 1 and 5 CloseLow Side Open Coil Close Coil Open Coil Close Coil Driver Q19 #3 #4 #7#8 3 and 7 Open 4 and 8 Close Low Side Open Coil Close Coil Open CoilClose Coil Driver Q20 #4 #3 #8 #7 4 and 8 Open 3 and 7 Close

The circuit 70 enables both recirculation and overlap by a more creativearrangement of the low side drivers. On any given cylinder the open coiland close coil do not share either a high side driver or a low sidedriver.

As shown above, the present invention reduces the number of gates andassociated driver circuitry required, thus reducing cost. Someembodiments described still permit simultaneous excitation andrecirculation. Of course, although a few arrangements have beendescribed, additional different arrangements utilizing the inventiveconcepts described herein could also be utilized.

In accordance with the provisions of the patent statutes andjurisprudence, exemplary configurations described above are consideredto represent a preferred embodiment of the invention. However, it shouldbe noted that the invention can be practiced otherwise than asspecifically illustrated and described without departing from its spiritor scope.

What is claimed is:
 1. A fuel injector control circuit comprising: aplurality of coils, including a first open coil for a first fuelinjector and an associated first close coil for the first fuel injector;a first gate connecting a first end of each of the first open coil andfirst close coil to a power supply; a second gate selectively connectinga second end of said first open coil to ground; and a third gateselectively connecting a second end of said first close coil to ground.2. The circuit of claim 1 wherein said open coil is activated based uponsaid first gate and said second gate being closed.
 3. The circuit ofclaim 2 wherein said close coil is activated upon said first gate andsaid third gate being closed.
 4. The circuit of claim 1 wherein saidplurality of coils further includes a second open coil and a secondclose coil, both for a second fuel injector, said second gateselectively connecting said second open coil to ground, said third gateselectively connecting said second close coil to ground.
 5. A fuelinjector control circuit comprising: a plurality of high side gates eachselectively connecting a different single open coil and a differentsingle close coil to a power supply; a plurality of low side gates, eachselectively connecting at least two of said coils to ground, including afirst low side gate selectively connecting at least two of said closecoils to ground, and a second low side gate selectively connecting atleast two of said open coils to ground.
 6. The circuit of claim 5wherein each said low side gate selectively connects at least four coilsto ground.
 7. The circuit of claim 6 wherein a first half of said lowside gates selectively connects at least four open coils to ground. 8.The circuit of claim 7 wherein a second half of said low side gatesselectively connects at least four close coils to ground.
 9. The circuitof claim 5 wherein said plurality of high side gates is twice as many assaid plurality of low side gates.
 10. The circuit of claim 9 whereineach of said plurality of low side gates selectively connects one fourthof the plurality of coils to ground.
 11. A method for controlling aplurality of fuel injectors including the steps of: a) associating eachof a plurality of pairs of coils with each of a plurality of fuelinjectors, each said pair comprising an open coil and a close coil; b)selectively connecting each of the pair of coils to a power source withone of a plurality of high side gates; c) selectively connecting atleast two of said open coils to ground with a first low side gate; d)selectively connecting at least two of said close coils to ground with asecond low side gate; e) activating each of said coils based uponactivation of a unique pair of one of said high side gates and one ofsaid low side gates.